A service called long term evolution (LTE) is known as one of the high-speed data communication specifications for mobile telephones. From the technical viewpoint of the antenna, the LTE has the following features.
That is, the LTE, which is a communication system called MIMO, achieves high-speed data communication by using a plurality of antennas in transmission and reception. A wireless communication device such as a mobile terminal using MIMO usually employs two antennas. Ideally, it is required that the antenna characteristics of the two antennas be equivalent.
As for the antenna characteristics of a MIMO antenna device, an index called antenna correlation is a key point. It is known that when a value (coefficient) of the antenna correlation is high (that is, the level of correlation is high), the communication speed is lowered.
PTL 1 proposes a multi-antenna applicable to a mobile communication system that is less affected by mutual coupling. This multi-antenna has a plurality of feed elements connected to a plurality of feed points on a circuit board and also has a single parasitic element or a plurality of parasitic elements connected to the circuit board in the vicinity of arbitrary feed points.